Automatic telephone-exchange system.



A. B. SPERRY.

AUTOMATIC TELEPHONE EXCHANGE SYSTEM. APPLICATION FILED NOV-26.1917.

1,280,324. Patented Oct. 1, 1918* //7 yen/0r;

4 777 40 5. Spam y fly W UNITED STATES PATENT OFFICE.

ARTHUR SPERRY, OF NEW YORK, N. Y., ASSIGNOR TO WESTERN ELECTRIC COMPANY, INCORPORATED, OF NEW YORK, N. Y., A CORPORATION OF NEW YORK.

AUTOMATIC TELEPHONE-EXCHANGE SYSTEM.

Specification of Letters Patent.

Patented Oct. 1, 1918.

Application filed November 26,1917. Serial No. 203,965.

To all whom it may concern:

Be it known that I, ARTHUR B. SPERRY, a citizen of the United States, residing at N ewYork, in the county of New York and State of New York, have invented certain new and useful Improvements in Automatic Telephone-Exchange Systems, of which the following is a full, clear, concise, and exact description.

This invention relates to trunking systems and more particularly to two-way two-wire trunks for use in automatic telephone systems, as, for example, for trunking between two automatic exchanges.

The object of this invention is to provide a two-way trunk having an improved and comparatively simple arrangement of circuits and apparatus' In accordance With this invention one feature is the provision of a two-way trunk line, which terminates at each end thereof in the multiple terminals of a non-numerical switch and also in the multiple terminals of a numerical switch. The seizure, at either end, of said trunk by a numerical switch serves automatically to start a non-numerical switch at the other end thereof operating to find the trunk and thus automatically extend the connection therefrom to an idle numerical switch, such for example as a selector or connector, according to the size or character of the exchange.

Another feature is the provision of means for rendering busy the test terminals of the trunk in the numerical switch at the called end thereof before the non-numerical switch at the same end has engaged the terminals of the trunk,

The invention may be more readily understood by reference to the accompanying drawing of a system embodying the invention,

Referring to the drawing, the two-Wire twowvay trunk terminates at the central office A in the multiple bank of a selector 2 and the multiple bank of a line finder switch 25, and at the central office B in the multiple bank of a selector 26 and in the multiple bank of a line finder 23.

The line finders 25 and 23 may be arranged to serve only trunk lines or may be arranged to serve both trunk lines and calling subscribers lines in their respective offlees. Similarly the selectors may be arranged to extend connections either to trunk lines only, or to called subscribers lines in their respective offices only, or to both. These arrangements are so well known in the art that further description is deemed unnecessary.

The arrangement of the apparatus is such that a call from the subscribers station C at office A for a subscribers station D at ofiice B, arrives at the bank terminals of the selector 2 at ofiice A and is extended through the office B by the line finder 23 and connector 24 thereat; In the opposite direction, calls over the same trunk arrive at the bank terminals of the selector 26 at the office B and are extended through the office A by means of'the line finder 25 and the conwill be seen, therefore, that each end of the trunk line terminates in an incoming and an outgoing switch and that the outgoing switch at one end cooperates with the incoming switch at the other end to extend a call.

The operation of the system is as follows: Assume that the subscriber at G whose line terminates at office A, desires to call the subscriber at station D, whose line terminates at oflice B. Cs telephone line is extended in the usual manner through the finder switch 1 and the brushes of the selector 2 to an idle trunk, the two wires 3 and 4: which are-connected to the contactterminals 10 and 11 respectively of the selector 2. Thereupon a circuit is closed for relay 5 from grounded battery right-hand winding of relay 5, lower left-hand winding of repeating coil 6, conductor 3, terminal 10, upper brush of selector '2, upper brush of line finder switch 1, the

gizes and connects ground to the multiple test terminal 12 of the selector 2 to render the trunk busy at oflice A. This ground is also extended to the line finder switch 1 to prevent in a well-known manner, therelease of these switches 1 and 2 until the calling subscriber replaces his receiver on the hook. Relay 7 also completes a circuit from grounded battery, winding of relay 13, right-hand armature and back contact of relay 14, armature and front contact of relay 7 to ground. Relay 13 by attracting its armatures connects the conductors 8 and 9 to conductors 15 and 16 respectively, thereby closing an operating circuit from ofiice to oflice B as follows: grounded battery, right-hand winding of relay l7, right-hand armature and back contact of relay 18, conductor 19, lower armature and back contact of relay 20, conductor 16, lower armature and front contact of relay 13, conductor 9, lower right-hand winding of repeating coil 6, right-hand armature and front contact of relay 5, upper right-hand winding of repeating COll 6, conductor 8, upper armature and front contact of relay 13, conductor 15, upper armature and back contact of relay 20, conductor 28, left-hand armature and back contact of relay 18, left-hand winding of relay 17 to ground. Relay 17 becomes energized and closes a circuit from grounded battery, left-hand winding of relay 21, left -hand armature and front contact of relay 17 to ground. Relay 21, by attracting its left-hand armature, connects ground to the multiple test terminal 22 of the selector 26, thereby rendering the trunk line busy at the oiiic'e B. It will be observed that the trunk is made busy before it is seized by the line finder 23. Relay 17 also closes a starting circuit in a well-known manner for operating the line finder 23. As

soon as the brushes of the line finder engage the terminals of the trunk, the movement of the line finder is stopped and a circuit for relay 18 is completed in a well-known manner for deenergizing relay 17. Relay 21, however, is held energized due to a locking circuit being completed in parallel with relay 18.

Circuits are now established for extending the connection from the connector 2% at otiice B to the called subscribers station D. The calling subscriber may now operate his dial and interrupt the above described circuit through relay 5. There is, therefore, a corresponding interruption of the circuit of the connector 2 1 at the right-hand armature and front contact of relay The connector 2% may thus be actuated in the usual manner from the dial at substation C to ex tend the connection to the called subscriber at station D. Relay 7. being of the slowrelease type. does not respond to the interruptions of its circuit produced by the operation of the calling subscribers dial.

Since the two wires 15 and 16 of the trunk line are inductivel connected throu h the repeating coil 6 at 0 cc A with the ca 1- ing line, a talking circuit is established between stations C and D as soon'as the su'b scriber at station D answers.

When the subscriber at station C replaces his receiver on the hook at the termination of conversation the circuit of relay 5 is opened, which causes this relay to deenergize and open the circuit of slow release relay 7. The circuit for this relay 7 is now held open for a sufficient length of time to cause it to-deenergize and disconnect ground from the multiple test terminal 12 of the selector 2. Line finder switch 1 and selector 2 will then release in the well-known manner.

The dee'nergization of relay 5 also opens the circuit over the trunk conductors l5 and 16, whereupon the holding circuits for mlays 21 and 18 may be opened in any one of the many well-known methods and hence further illustration and description thereof is deemed unnecessary.

Calls originatin in ofiice B are extended to subscribers in 0 cc A in the same manner.

-What is claimed is:

1. In an automatic telephone exchange system, two central oflices, incoming and outgoing switches at each of said ofiices, and a two-wire trunk extending between said ofiices and terminating in contacts of the multiple terminal banks of said incoming and outgoing switches.

2. In an automatic telephone exchange system, two central oflices, line finder and selector switches at each ofiice, and a twowire trunk extending between said offices, terminating in the contacts of the multiple terminal bank of said line finder switches and in the contacts of the multiple terminal bank of said selector switches.

3. In an automatic telephone exchange system, two central ofiices, a two-wire trunk extending between said ofiices and terminating at each oflice in contacts of a plurality of multiple terminal banks, and means operated by the seizure of said trunk at either of said offices for placing the contacts of one of the multiple banks at the other otlice in a different electrical condition from that of the contacts of another of said multiple banks at said last mentioned otlice.

1. In an automatic telephone exchange system, two central ottices, a two-wire trunk extending between said otiices and terminating at each of said oi'lices in contacts of two multiple terminal banks, and means operated by the seizure of said trunk at either of said otlices for rendering said trunk selectable at the contacts of one of the multiple banks at the other office and non-selectable at the contacts of the other multiple bank at said last mentioned ofiice.

' 5. In an automatic telephone exchange for rendering said trunk selectable by a line system, two central offices, line finder and finder switch at the other office and nonselector switches at each of said ofiices, a selectable by a selector switch at said last two-wire trunk extending between said ofmentioned ofiice. 5 fices and terminating in the contacts of the Inwitness whereof, I hereunto subscribe 15 multiple terminal bank of said line finder my name this 21st day of November, A. D., switches and in the contacts of the multiple 1917.

dterminal bank of said selector switches, and ARTHUR B.-SPERRY.

means operated by the-seizure of said trunk Witness:

10 by a selector switch at either of said oflices CYRIL W. KEENE. 

